Laser surgery apparatus and method

ABSTRACT

An argon-fluoride excimer laser or other laser source capable of generating far-ultraviolet radiation at 193 nm is pulsed with energy densities of greater than 20 mj per cm 2  at a repetition rate up to 25 pulses per second to direct its radiation through a mask and onto corneal tissue, or other biological matter, to form an ablation therein of predetermined configuration and depth by a process of ablative photodecomposition. The masks are formed with a slit, circular, crescent or other openings of widths between 30 and 800 microns, and may even be formed to provide a graded intensity center to edge. The mask is reflective or composed of or faced with an organic polymer to prevent heat build-up. Each micron of the depth of a 200 micron deep groove formed in corneal tissue, for example, resulted from the application of 1 joule per square centimeter of radiation, from a series of pulses delivered at intensities of between 100 mj and 200 mj per square centimeter, and at a laser pulse rate of between 1 and 25 Hertz, the entire groove taking 100 seconds.

This is a Division of application Ser. No. 08/341,207 filed on Dec. 5,1994 pending, which is a Division of application Ser. No. 07/893,841filed on Jun. 4, 1992, ABD, which is a Continuation of application Ser.No. 07/673,541 filed on Mar. 18, 1991, now abandoned, which is aContinuation of application Ser. No. 07/109,812 filed on Oct. 16, 1987,now U.S. Pat. No. 5,108,388, which is a Continuation of application Ser.No. 06/859,212 filed on May 2, 1986, ABD, which is a Continuation ofapplication Ser. No. 06/561,804 filed on Dec. 15, 1983, ABD.

BACKGROUND OF THE INVENTION--FIELD OF APPLICATION

This invention relates to surgical apparatus and methods; and moreparticularly to laser source surgical apparatus and methods.

BACKGROUND OF THE INVENTION--DESCRIPTION OF THE PRIOR ART

Surgical procedures, especially surgical procedures wherein animalbiological tissue, human biological tissue, or other matter are to beremoved from a predetermined area and to a predetermined depth, requiregreat surgical skill. In such procedures the skill of the surgeon isoften enhanced by the use of apparatus particularly designed forsurgical purposes. Such apparatus is more often than not very expensive,and in many instances requires complex procedures and a highly skilledor trained operator. Regardless of the expense of the apparatus,complexity of the procedure, or skill or training required to use theapparatus, it is often the availability of the apparatus that makes aparticular surgical procedure possible. However, quite often theapparatus and associated surgical method, while facilitating aparticular surgical procedure, produce unwanted effects on or to areasof the human or animal adjacent to those requiring the surgery.

Laser source apparatus has been utilized for surgical procedures,especially in ophthalmology. In such apparatus, a collimated beam oflight, generated or produced by the laser source, is directed so as tofocus on the area to be operated on. The light energy produced by thelaser is converted to heat energy which, in turn, is utilized for thesurgery. Such laser source facilitated surgical procedures are sometimesand may be otherwise referred to as thermal photocoagulation, as a finecontrolled burn is produced. Other laser systems focus high poweredpulses of light of sufficient intensity to produce optical (ordielectric) breakdown. This produces a surgical effect referred to asphotodisruption because the tissues are "disrupted" by the pulsar burnand associated shock wave.

Some available laser source apparatus for those surgical purposes, andassociated surgical procedures, are described: in U.S. Pat. No.3,982,541 granted on Sep. 28, 1976 to F. A. L'Esperance, Jr., for EyeSurgical Instrument; in U.S. Pat. No. 4,309,998 granted on Jan. 12, 1982to D. S. Aron nee Rose et al for Process And Apparatus For OphthalmicSurgery; in U.S. Pat. No. 4,336,809 granted on Jun. 29, 1982 to W. G.Clark for Human And Animal Tissue Photoradiation System And Method; andin U.S. Pat. No. 4,391,275 granted on Jul. 5, 1983 to F. Frankhauser, etal for Method For the Surgical Treatment Of The Eye.

However, utilization of such apparatus, more often than is desired,effects unwanted changes in adjacent remaining structures, causesthermal damage to areas adjacent the area requiring the surgicalprocedure, and results in undesirable irregular edges of the interactionsite produced by the forces of optical breakdown. In addition, not everylaser is suitable or acceptable if the surgeon is seeking the bestpossible results from the surgical procedures.

A new tissue interaction has been observed using pulsed ultravioletlight. A direct photochemical effect is observed which interactsexclusively with the irradiated tissues and produces no discernibleeffect upon the adjacent, unirradiated tissues. For lasers generatingultraviolet wavelengths shorter than 193 nm (nanometers), it has beenfound that optical delivery systems become extremely difficult to buildbecause of the limited availability of refracting material. For lasersgenerating wavelengths longer than 200 nm, thermal effects become moredominant and the percentage of true ablative photodecomposition lessens.

Surgical procedures may be performed using pulsed ultraviolet lightutilizing a mix of complete photoablation with some thermal effect asdesired by the operating surgeon.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a new andimproved laser source surgical apparatus.

It is another object of this invention to provide a new and improvedmethod of laser surgery.

It is yet another object of this invention to provide a new and improvedlaser source apparatus for producing ablative photo-decomposition inophthalmic surgery.

It is still another object of this invention to provide a new andimproved method for surgery utilizing a far-ultraviolet laser sourcewhich produces ablative photodecomposition.

It is yet still another object of this invention to provide a new andimproved laser source apparatus for ophthalmological surgery.

It is yet still another object of this invention to provide a new andimproved method for laser source ophthalmological surgery.

It is a further object of this invention to provide a new and improvedsurgical apparatus utilizing a far-ultraviolet laser.

It is still a further object of this invention to provide a new andimproved surgical method utilizing a far-ultraviolet argon-fluorideexcimer laser.

This invention involves surgical apparatus and methods utilizing a lasergenerated light at particular wavelengths to effect ablativephotodecomposition of particular areas of animal or human biologicalmatter to a particular depth; and contemplates utilizing a laserproducing far-ultraviolet radiation at a wavelength of 193 nm(nanometers) and directing the same to the particular area through amask of predetermined configuration and in pulses of predeterminedintensity for predetermined time periods so as to produce an opening ofsharply defined edges and depth.

Other objects, features and advantages of the invention in its detailsof construction and arrangement of parts will be seen from the above,from the following description of the preferred embodiment whenconsidered with the drawings and from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic illustration of a photoablation apparatus andsystem incorporating the instant invention;

FIG. 2 is a schematic illustration of a laser delivery system for usewith the apparatus and system of FIG. 1;

FIG. 3 is a schematic illustration of an ophthalmic delivery system foruse with the apparatus and system of FIG. 1;

FIG. 4 is a plan view of a mask usable with the apparatus and system ofFIG. 1;

FIG. 5 is a plan view of another mask useable with the apparatus andsystem of FIG. 1;

FIG. 6 is a sectional view through a mask useable with the apparatus andsystem of FIG. 1;

FIG. 7 is a sectional view of another mask usable with the apparatus andsystem of FIG. 1;

FIG. 8 is a sectional view of yet another mask usable with the apparatusand system of FIG. 1;

FIG. 9 is a sectional view through the schematic eye of FIG. 1 duringthe surgical procedure according to the instant invention,

FIG. 10 is a sectional view through the schematic eye of FIGS. 1 and 9following the surgical procedure according to the instant invention;

FIG. 11 is a sectional view perpendicular to a groove formed byphotoablation according to the instant invention using the mask of FIG.4; and

FIG. 12 is a schematic view perpendicular to a V-shaped groove formed byphotoablation according to the instant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For convenience, the invention will be described as applied to a laserphotoablation and method utilizing an argon-fluoride excimer laser whichgenerates far-ultraviolet radiation at 193 nm (nanometers) atpredetermined pulse energy densities and repetition rates.Far-ultraviolet light may he produced by other lasers to be incorporatedinto this ophthalmic surgical system. Furthermore, the wavelengths oflight applicable extend to 248 nm in spite of the less purephotodecomposition noted. The laser beam is thereafter directed througha mask formed from particular material and with one or more slit orcircular openings to impinge upon an area of the cornea of an eye toform therein a groove of predetermined peripheral configuration anddepth. It should be understood that without departing from theinvention: the mask openings can be of any convenient peripheralconfiguration; the masks may be formed of any appropriate material; afiber-optic pipe and rod delivery system may be utilized without masks,and the apparatus and system may be utilized for procedures on othertissues and biological matter, such as dental caries, human skin, andthe like.

With reference to FIG. 1, there is generally shown at 20 a photoablationlaser surgery apparatus and system utilizing a laser delivery system 22and associated power supply and control system 24 by which a laser beam26 is directed through openings 28 formed in a mask 30 and onto thecornea 32 of an eye 34, of either a human or an animal.

Laser delivery system 22 includes an argon-fluoride excimer laser suchas one currently manufactured by Lamda Physik as their Model 201E.However, it is understood that other laser sources may be used toproduce the effective ultraviolet light. Laser system 22 generates alaser beam 26 in the far-ultraviolet range of 193 nm (nanometers). Otherranges of ultraviolet wavelengths may be chosen. Power supply andcontrol 24 is conventionally available and is interconnected to lasersystem 22 so that the output thereof is pulsed at pulse energy densitiesof greater than 420 mj per cm² (milijoules per square centimeter) at arepetition rate up to 25 pulses per second.

FIG. 2 illustrates a laser delivery system 50 wherein an ultra-violetlaser beam 52 is directed through lens 54 and then through a passage 56and opening 58. An appropriate opening 60 is provided to passage 56 forinfusion of nitrogen or other similar gases. Another opening 62 isprovided for passage 56 to provide a high vacuum therefor.

In FIG. 3, there is shown an ophthalmic delivery system 80 forgenerating and delivering a laser generated ultra-violet laser beam 82through a variable slit 84 to and through a lens 86, through an aperture88, through another lens 90, and onto an area, such as an eye 92, uponwhich a surgical procedure is to be performed.

Mask 30 (FIGS. 1 and 4) is formed from aluminum, or other appropriatematerial, and includes a number of slits 100 formed therethrough. Theslits 100 range in width from 150 to 800 microns. While four slits havebeen shown for mask 30, it should be understood that a lesser or greaternumber of slits can be provided for mask 30 and that the widths as wellas the slit configuration can be appropriately selected. An alternatemask 110, shown in FIG. 5, is formed with seven holes 112 drilled orotherwise formed therethrough. Holes 112 range in diameter from 100microns to 750 microns. It should be understood that openings of anydesired configuration (crescents, concentric rings, etc.) may be formedthrough masks 30 and 110. In addition, the mask may also be formed toprovide a graded intensity center to edge or edge to center. The maskmay be clad or covered with plastic or other polymers to prevent heatingof the mask. The organic material will prevent ultra-violet light fromstriking the mask and heating it directly. The cladding prevents heatingby being ablated by the ultraviolet light which is being shielded fromthe eye.

In FIG. 6, there is shown a mask 120 with an opening 122 and having asurface of 2000° A chrome formed onto a base 124 of poly methylmethacrylate to reflect the ultra-violet light and to prevent heating.The mask is stabilized by a vacuum seal.

In FIG. 7, there is a mask 130 with an opening 132.

FIG. 8 shows still another alternate mask 140 with an opening 142. Mask140 includes one or more metal cooling vanes 144 separated by an airspace 146 from, but otherwise carried by or supported with respect to, abase 148 of stainless steel; all being stabilized by a vacuum seal.

While masks 120, 130, and 140 have been shown with single openings 122,132, 142, respectively, it should by understood that any suitable numberof openings may be formed in the masks, and that such openings may beformed with any appropriate configuration and width.

In use, laser apparatus 20 is positioned with respect to the area oftissue, biological matter, or the like upon which the surgical procedureis to be performed. In this instance, laser 20 is disposed with respectto cornea 32 of an eye 34 so that laser beam 26 will be directed towardsmask 30 and then upon cornea 32. The output of laser 20 is delivered ina series of pulses under control of laser delivery system 22 and laserpower supply and control system 24. For each micron depth of cornealtissue to be ablated, one joule per square centimeter was applied. Thusin forming a 200 micron deep groove, for example, 200 joules per cm²would be required. This was delivered in a series of pulses varying inintensity between 100 and 200 mj per square centimeter depending uponthe area of the final focus of laser apparatus 20.

The laser pulse rate for apparatus 20 was between 1 and 25 Hertz and thepulses were delivered until sufficient total energy achieved the desireddepth of cut. The maximum exposure time for the complete section of thecornea as described required 100 second (700 mj per cm²). More rapidpulse rates create tissue heating distortion from gas pressure backup inthe irradiated area. Higher energy densities in the irradiated areaproduce unwanted shock effects.

In FIG. 9, eye 34 is shown during the above described procedure andillustrates the bond breaking occurring at 150 in the epithelium 152 andstromal collagen 154. In FIG. 10, the ablated groove 160 is shown.

It should be noted that, by utilizing apparatus 20 and the describedprocedure, a groove 200 (FIG. 11) can be formed with parallel walls 202and a square bottom 204.

Alternatively, a V-shaped groove 210 (FIG. 12) may be formed byapparatus 20 and the described procedure by directing laser beam 28 sothat it strikes cornea 32 obliquely. By doing so, the energydistribution across a slit or other opening formed through mask 30 willcause the tissue to ablate more rapidly at one edge.

The described apparatus 20 and method causes a specific photo-chemicalreaction and results in the ablation of corneal or other tissues withoutthermal damage to the adjacent remaining structures. The method allowsincisions of controlled depth and shape. Defined volumes of tissue canbe removed by masking to control the area ablating the tissue to apredetermined depth.

The corneal epithelium, for example, shows an extreme sensitivity to the193 nm light emitted by the argon-fluoride excimer laser of apparatus20. During the resulting ablative photodecomposition, the tissue isbroken into smaller volatile fragments by direct photo-chemicalinteraction without heating the remaining adjacent tissues. Ultravioletlight at 193 nm is highly energetic, each photon having 6.4 electronvolts. The high energy of each photon directly breaks intramolecularbonds.

Laser systems generating wavelengths larger than 193 nm thermallyvaporize tissues with changes in adjacent remaining structures whilelaser systems generating wavelengths shorter than 193 nm are difficultto build because of the limited availability of refracting material.Tissues sectioned with a frequency double YAG laser run in a thermalmode show irregular edges of the interaction side produced by hightissue temperatures.

Apparatus 20 and the described method will produce an incisionresembling that formed by a surgical cut. There will be a parallelbetween the gross corneal appearance and the mask, and no distortion ofthe stromal lamellae or epithelial edge. The groove walls will beparallel along their entire length and have a squared bottom.

The ablative photodecomposition accomplished by the described apparatusand method will provide grooves of a precisely determined shaped and toa precisely determined depth. This has the same clinical indication aslamellar keratectomy, since precise excision of the corneal tissue canbe accomplished. In addition, a controlled penetrating corneal incisioncan, in principal, be done for corneal transplantation.

Radial incisions as well as concentric rings and crescents can beaccomplished with the described apparatus and method. In fact, the laserlight of the described method and apparatus can be applied to a circularmask of graded intensity center to edge. This would take away moretissue either centrally or peripherally depending on the distribution oflight. The net effect would be either to steepen or flatten the cornea.The ability to make controlled radial incisions, or to selectively shapethe corneal surface, allows modification of the refractive status of theeye.

As a further modification, apparatus 20 can be provided with afiber-optic pipe or rod delivery system to allow placement of UV laserlight to intraocular structures. This would allow (a) controlledfiltering operation for glaucoma to be done subconjunctivally or via theanterior chamber; and (b) a "phakoemulsification" to be done with pulsedultraviolet light rather than a vibrating titanium rod; (c) placement ofthe unit in the eye to section vitreous membranes as an alternative torotating or oscillating knives.

Additionally, such a fiber-optic rod delivery system can be used in thetreatment of dental caries by directing the light to the affected areaor can be used in the removal of skin lesions.

As various possible embodiments might be made of the above invention,and as various changes might be made in the embodiments above set forth,it is to be understood that all matter herein described or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense. Thus, it will be understood by those skilled in the art,although preferred and alternative embodiments have been shown anddescribed in accordance with the Patent Statutes, the invention is notlimited thereto or thereby, since the embodiments of the inventionparticularly disclosed and described hereinabove are presented merely asan example of the invention. Other embodiments, forms, and modificationsof the invention, coming within the proper scope and spirit of theappended claims, will of course readily suggest themselves to thoseskilled in the art. Thus, while there has been described what is atpresent considered to be the preferred embodiments of this invention, itwill be obvious to those skilled in the art that various changes andmodifications may be made therein, without departing from the invention,and it is, therefore, aimed in the appended claims to cover all suchchanges and modifications as fall within the true spirit and scope ofthe invention, and it is understood, although I have shown the preferredform of my invention, various modifications may be made in the detailsthereof, without departing from the spirit as comprehended by thefollowing claims.

What is claimed is:
 1. A system for use in a laser source surgicalmethod of removing corneal tissue from a cornea, said system comprisinga mask having an aperture for providing a graded intensity to the corneafrom center to edge with more intensity at the center than at the edge.2. The system according to claim 1, further comprising a laser deliverysystem.
 3. A system according to claim 1 wherein said aperture iscircular and has a variable diameter.
 4. A system according to claim 1wherein said mask has a plurality of circular apertures.
 5. A systemaccording to claim 1 wherein said aperture is circular.
 6. A systemaccording to claim 1 wherein said aperture has a variable diameter. 7.The system according to claim 1, further comprising a laser thatproduces radiation at a wavelength of 193 nanometers in a series ofpulses.
 8. The system according to claim 7, wherein the laser and laserdelivery system deliver energy to the cornea in the range of 100 to 200millijoules per square centimeter.
 9. A system according to claim 7,wherein said system delivers pulses at a rate of from 1 Hertz to 25Hertz.
 10. A system according to claim 7, wherein the mask is formedfrom an ablatable material.
 11. A system according to claim 10, whereinsaid ablatable material is a plastic or other polymer.
 12. A systemaccording to claim 7, wherein said mask comprises a base and at leastone cooling vane which is separated from said base by an air space. 13.A system according to claim 12, wherein said at least one cooling vaneis formed from metal.
 14. A system for use in a laser source surgicalmethod of removing corneal tissue from a cornea, said system comprisinga mask having an aperture for providing a graded intensity to the corneafrom edge to center with more intensity at the edge than at the center.15. A system according to claim 14 wherein said mask has a plurality ofapertures.
 16. A system according to claim 14, further comprising alaser that produces radiation at a wavelength of 193 nanometers in aseries of pulses.
 17. A system according to claim 14, further comprisinga laser delivery system.
 18. A system according to claim 16, wherein thelaser and the laser delivery system deliver energy in the range of 100to 200 millijoules per square centimeter.
 19. A system according toclaim 16, wherein said system delivers pulses at a rate of from 1 Hertzto 25 Hertz.
 20. A system according to claim 16, wherein the mask isformed from an ablatable material.
 21. A system according to claim 20,wherein said ablatable material is a plastic or other polymer.
 22. Asystem according to claim 16, wherein said mask comprises a base and atleast one cooling vane which is separated from said base by an airspace.
 23. A system according to claim 22, wherein said at least onecooling vane is formed from metal.